paying more than i am supposed to

hi<br> i took a laptop from dot fnb and i was supposed to get charged R685 but for the past 3 months i am getting charged R699. i tried phoning them but they never answer. i emailed the man responsible on 12 january 2015 and he rep**** on 13 january 2015. he said \i will look into the matter and give you a call". i am still waiting for that call. 2 weeks no reply from him. i emailed him again on 26 january 2015 and he hasnt rep**** to that either. """